Anemia is caused by a deficiency of iron. Iron is an essential mineral that is needed by the body to produce hemoglobin, a protein in red blood cells that carries oxygen from the lungs to the rest of the body. When there is not enough iron available, the body is unable to produce enough healthy red blood cells, leading to anemia.

Option 1: Cobalt is not directly related to anemia. Cobalt is a trace mineral that is needed in very small amounts by the body. It is a component of vitamin B12, which is important for red blood cell production, but a deficiency in cobalt alone would not cause anemia.

Option 3: Sodium is not directly linked to anemia. Sodium is an electrolyte and is involved in maintaining proper fluid balance, but it does not play a role in red blood cell production or preventing anemia.

Option 4: Calcium is not directly associated with anemia. Calcium is a mineral that is important for bone health, muscle function, and other processes in the body, but it is not directly involved in the production of red blood cells or the development of anemia.

Alert - correct answer should be: Option 2 Iron